Optical system and its design method

Abstract

An optical system and its design method are disclosed, which include: a spectral chip and an optical component held on the sensing path of the spectral chip. The spectral chip includes a photoelectric detection layer and a light modulation layer located on the sensing path of the photoelectric detection layer. The photoelectric detection layer obtains a light signal modulated by the modulation layer from the incident light signal. The optical component is configured to receive the light signal from the object to be photographed and guide the light signal to the spectral chip. Wherein, the optical component makes the light signals guided to each position of the spectral chip have a main ray included angle with a fixed angle and a light collection cone angle with a predetermined angle, and the predetermined angle is less than or equal to 45°. In this way, through the optical component with a specific structural configuration, the main light angle and the light collection cone angle of each pixel point of the spectral chip are fixed and within a preset range, so as to reduce the spectral recovery error of the spectral chip.

Description

Technical Field

[0001] This application relates to a spectral chip, and particularly to an optical system including the spectral chip and its design method. Background Art

[0002] When light interacts with matter, such as absorption, scattering, fluorescence, Raman, etc., specific spectra will be generated, and the spectrum of each substance is unique. Therefore, spectral information can be said to be the "fingerprint" of all things.

[0003] A spectrometer can directly detect the spectral information of a substance to obtain the presence status and chemical composition of the measured target, and it is one of the important test instruments in the fields of material characterization, chemical analysis, etc. From the perspective of technological development, micro spectrometers can be divided into four categories: dispersive type, narrowband filtering type, Fourier transform type, and computational reconstruction type.

[0004] A dispersive spectrometer generally consists of one or more diffraction gratings, an optical path, and a photodetector array. Among them, the optical signal from the measured target is collimated and irradiated on the diffraction grating through the entrance slit. The diffraction grating disperses the spectral components in different directions, and finally the concave mirror focuses the dispersed spectral components on the photodetector array to obtain the spectral distribution. This type of spectrometer has ultra-high resolution, a wide spectral range, and mature technology. However, the dispersive spectrometer depends on its bulky dispersive elements, long optical path, etc., and it is difficult to achieve size compression.

[0005] The narrowband filtering type spectrometer can selectively transmit light of a specific wavelength to achieve spectral detection. Its device is planar and does not require a long optical path, having some advantages in system miniaturization. In the narrowband filtering type spectrometer, the filter used for wavelength selection is a band-pass filter. The higher the spectral resolution, the narrower and more filters must be used, which increases the volume and complexity of the entire system. At the same time, when the spectral response curve becomes narrower, the light flux decreases, resulting in a lower signal-to-noise ratio.

[0006] The Fourier transform type spectrometer is usually used for the measurement of infrared absorption or emission spectra. By performing a Fourier transform on the interferogram obtained by the detector, the spectrum to be measured is obtained, having the advantages of high signal-to-noise ratio, small size, and low cost. However, the Fourier transform type spectrometer needs to rely on an external camera to perform scattering imaging on the interferogram, which is not conducive to further miniaturization.

[0007] With the development of computer technology, a new type of spectrometer has emerged in recent years: the computational reconstruction type spectrometer, which approximates or even reconstructs the spectrum of the incident light through calculation. The computational reconstruction type spectrometer can relatively better solve the problem of the decline in detection performance caused by miniaturization.

[0008] Since computational reconstruction spectrometers or computational reconstruction spectral imaging devices belong to emerging technologies, in practical applications, computational reconstruction light source spectrometers or computational reconstruction spectral imaging devices encounter many technical problems. Discovering and solving these technical problems is the only way to promote the maturation of computational reconstruction spectrometers and spectral imaging devices. Summary of the Invention

[0009] One advantage of the present application is to provide an optical system and a design method thereof. The optical system includes a spectral chip and an optical component held on the sensing path of the spectral chip. The optical component has a structural configuration such that the principal light angle of the optical signal guided to each position of the spectral chip is a fixed value and the light collection cone angle of each position is a predetermined value. In this way, through the optical component with a specific structural configuration, the light collection cone angle of each pixel of the spectral chip is controlled to be a predetermined value within a preset range and / or the principal light angle of each pixel is a fixed value, so as to reduce the spectral recovery error of the spectral chip.

[0010] Through the following description, other advantages and features of the present application will become apparent and can be achieved by the means and combinations specifically pointed out in the claims.

[0011] To achieve at least one of the above advantages, the present application provides an optical system, which includes:

[0012] A spectral chip, including a photoelectric detection layer and a light modulation layer located on the sensing path of the photoelectric detection layer. The photoelectric detection layer is configured to obtain the optical signal modulated by the light modulation layer from the incident optical signal; and

[0013] An optical component held on the sensing path of the spectral chip, the optical component being configured to receive the optical signal from the object to be photographed and guide the optical signal to the spectral chip;

[0014] Wherein, the optical component is configured such that the principal light angle of the optical signal guided to each position of the spectral chip is a fixed value and the light collection cone angle of each position is a predetermined value.

[0015] In the optical system according to the present application, the predetermined value is less than or equal to 45°.

[0016] In the optical system according to the present application, the predetermined value is less than or equal to 35°.

[0017] In the optical system according to the present application, the predetermined value is less than or equal to 10°.

[0018] In the optical system according to the present application, the optical component includes a lens group, and the F-number of the lens group is greater than or equal to 1.8.

[0019] In the optical system according to the present application, the F-number of the lens group is greater than or equal to 2.5.

[0020] In the optical system according to the present application, the optical component further includes a diaphragm for adjusting the F-number of the lens group.

[0021] In the optical system according to the present application, the lens group has a field of view angle θ and an image height h, where the optical system satisfies the following relationship:

[0022] L / h * tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the object to be photographed, and L is the side length of the effective sensing area of the spectral chip.

[0023] In the optical system according to the present application, X is less than or equal to 6 cm and Y is less than or equal to 10 cm. When X is less than or equal to 6 cm and Y is less than or equal to 10 cm, the spectral chip is adapted to be configured to collect the optical frequency information in the optical signal from the object to be photographed.

[0024] In the optical system according to the present application, the optical component includes a light homogenizing module and a collimating unit located on the light output path of the light homogenizing module. The light homogenizing module is configured to homogenize the optical signal from the object to be photographed, and the collimating unit is configured to collimate the homogenized optical signal.

[0025] In the optical system according to the present application, the light homogenizing module includes a diffusing element and a diaphragm located on the light output path of the diffusing element. The diaphragm has a light passing hole, and the size of the light passing hole is 1 mm to 10 mm.

[0026] In the optical system according to the present application, the light homogenizing module includes an integrating sphere, the integrating sphere has a light input port and a light output port, and the size of the light output port is smaller than the size of the light input port.

[0027] In the optical system according to the present application, the light homogenizing module includes a diaphragm, a scattering element located on the light output path of the diaphragm, and a light homogenizing rod located on the light output path of the scattering element.

[0028] In the optical system according to the present application, the light homogenizing module further includes at least one optical lens located on the light input path of the diaphragm.

[0029] In the optical system according to the present application, the optical component includes a telecentric lens.

[0030] According to another aspect of the present application, there is also provided a design method of an optical system, which includes:

[0031] Obtain the conversion matrix of the photoelectric detection layer of the spectral chip. The photoelectric detection layer obtains the detected optical signal from the incident optical signal based on the conversion matrix. Wherein, the spectral chip further includes an optical modulation layer located on the sensing path of the photoelectric detection layer; and

[0032] Determine the structural configuration of the optical component based on the numerical change of the conversion matrix. The structural configuration is used to make the principal optical angle of the optical signal guided to each position of the spectral chip a fixed value and the light-receiving light cone angle of each position a predetermined value. Wherein, the optical component is held on the sensing path of the spectral chip for receiving the optical signal from the photographed target and guiding the optical signal to the spectral chip.

[0033] In the design method of the optical system according to the present application, the predetermined value is less than or equal to 45°.

[0034] In the design method of the optical system according to the present application, the predetermined value is less than or equal to 35°.

[0035] In the design method of the optical system according to the present application, the predetermined value is less than or equal to 10°.

[0036] In the design method of the optical system according to the present application, the optical component includes a lens group, and the F-number of the lens group is greater than or equal to 1.8.

[0037] In the design method of the optical system according to the present application, the F-number of the lens group is greater than or equal to 2.5.

[0038] In the design method of the optical system according to the present application, the lens group has a field of view angle θ and an image height h. Wherein, the optical system satisfies the following relational expression:

[0039] L / h*tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the photographed target, and L is the side length of the sensing effective area of the spectral chip.

[0040] Through the understanding of the subsequent description and drawings, the further objects and advantages of the present application will be fully embodied.

[0041] These and other objects, features and advantages of the present application will be fully embodied through the following detailed description, drawings and claims. Description of the Drawings

[0042] The above and other objects, features, and advantages of the present application will become more apparent by describing the embodiments of the present application in more detail with reference to the accompanying drawings. The drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation to the present application. In the drawings, the same reference numerals generally represent the same components or steps.

[0043] Figure 1 The figure shows a schematic diagram of a spectral chip for calculating a reconfigurable spectrometer according to an embodiment of the present application.

[0044] Figure 2A The figure shows one of the schematic diagrams of the performance curve of the spectral chip according to an embodiment of the present application.

[0045] Figure 2B The figure shows another schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0046] Figure 2C The figure shows a third schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0047] Figure 2D The figure shows a fourth schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0048] Figure 2E The figure shows a fifth schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0049] Figure 2F The figure shows a sixth schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0050] Figure 2G The figure shows a seventh schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0051] Figure 2H The figure shows an eighth schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0052] Figure 2I The figure shows a ninth schematic diagram of the performance curve of the spectral chip according to an embodiment of the present application.

[0053] Figure 3 The figure shows a schematic diagram of an optical system according to an embodiment of the present application.

[0054] Figure 4 The figure shows a schematic diagram in which the optical components of the optical system according to an embodiment of the present application are implemented as a lens group.

[0055] Figure 5The figure shows a schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a light homogenizing component.

[0056] Figure 6 The figure shows another schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a light homogenizing component.

[0057] Figure 7 The figure shows still another schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a light homogenizing component.

[0058] Figure 8A The figure shows a schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a telecentric lens.

[0059] Figure 8B The figure shows another schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a telecentric lens.

[0060] Figure 8C The figure shows still another schematic diagram in which the optical component of the optical system according to an embodiment of the present application is implemented as a telecentric lens. Detailed implementation manners

[0061] Next, exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all embodiments of the present application. It should be understood that the present application is not limited by the exemplary embodiments described herein.

[0062] Summary of the Application

[0063] As mentioned above, a spectrometer can directly detect the spectral information of a substance and obtain the presence status and chemical composition of the measured target, and is one of the important test instruments in the fields of material characterization, chemical analysis, etc. From the perspective of technological development, micro spectrometers can be divided into four categories: dispersive type, narrowband filtering type, Fourier transform type, and computational reconstruction type.

[0064] A computational reconstruction type spectrometer (hereinafter referred to as a computational spectrometer) or a computational reconstruction type spectral imaging device is a new type of spectrometer or spectral imaging device that has emerged in recent years with the development of computer technology. Most of the following embodiments are described by taking a spectrometer as an example. The computational reconstruction type spectrometer can relatively better solve the problem of the decline in detection performance caused by miniaturization.

[0065] However, since the computational reconstruction type spectrometer belongs to an emerging technology, in practical applications, the computational reconstruction type light source instrument encounters many technical problems. Discovering and solving these technical problems is the only way to promote the maturation of the computational reconstruction type spectrometer.

[0066] More specifically, existing computational spectrometers generally work in the following manner: First, a spectral chip is used to obtain the optical signal from the target to be measured, and then the acquired optical information is processed based on a specific algorithm to obtain the spectral information of the target to be measured. By way of example but not limitation, during this process, the spectral chip can capture the information in the optical signal of the target to be measured in the optical frequency domain to be measured, and the implementation methods include: using a photodetector array with an optical modulation structure, or combining a filter element array with a photodetector array, where the filter element array can perform broadband filtering processing on the optical information in the frequency domain or wavelength domain.

[0067] Compared with traditional spectrometers (e.g., narrowband filtering spectrometers), at least one filter element in a computational spectrometer uses a broadband filter, which makes the data detected by the computational spectrometer system look completely different from the original spectrum. However, through the application of a computational reconstruction algorithm, the original spectrum can be restored computationally. Since more light passes through the broadband filter than the narrowband filter, a computational spectrometer can detect the spectrum from a darker scene, such as taking a night scene. In addition, according to the theory of compressive sensing, the spectral curve of the filter element can be appropriately designed to probabilistically restore the sparse spectrum with a number of filter elements much smaller than the number of expected spectral channels (restoring a higher-dimensional vector from a lower-dimensional vector), which is undoubtedly very beneficial for miniaturization. On the other hand, by using a larger number of filter elements, a regularization algorithm (obtaining a denoised lower-dimensional vector from a higher-dimensional vector) can be used to reduce noise, which increases the signal-to-noise ratio and makes the entire system more robust.

[0068] Relatively speaking, when designing a traditional spectrometer, a filter needs to be designed according to the required wavelength (the effect is also equivalent to the optical modulation structure of the spectral chip) so that light of a specific wavelength can pass through (generally, it is designed to enhance the projection of incident light of a specific wavelength, rather than incident light of a non-specific wavelength band cannot be projected. By changing the structure period and diameter of nanodisks, etc., the resonance conditions can be controlled, and the central wavelength of the incident light that can be enhanced in projection can be changed, thereby realizing the filtering characteristics). That is, during the design process of a traditional spectrometer, it is necessary to focus on controlling the size and position accuracy of the optical modulation structure, and at the same time, find ways to improve its transmittance at a specific wavelength. For a computational spectrometer, what is needed is to be able to receive light in a relatively large wavelength range (e.g., 350 nm to 900 nm), so more attention needs to be paid to the refractive index during design.

[0069] Figure 1 The figure shows a schematic diagram of a spectral chip for a computational reconstruction spectrometer according to an embodiment of the present application. As Figure 1The spectral chip shown schematically is a spectral chip disclosed by the inventor of the present application in Chinese Patent CN201921223201.2. Based on the content of Chinese Patent CN201921223201.2, the spectral chip 100 includes a photoelectric detection layer 110 and an optical modulation layer 120 held on the sensing path of the photoelectric detection layer 110. In particular, the optical modulation layer 120 includes at least one modulation unit 121, and each modulation unit 121 corresponds to at least one induction unit 111 of the photoelectric detection layer 110. Among them, the spectral chip 100 uses the modulation unit 121 of the optical modulation layer 120 to modulate the optical signal from the measured target to obtain a modulated optical frequency signal, and uses the photoelectric detection layer 110 to receive the modulated optical frequency signal and provide a differential response thereto. Then, the signal circuit processing layer of the spectral chip 100 reconstructs the differential response to obtain the original spectral information of the measured target. In some specific examples, the optical modulation layer 120 includes at least one modulation unit 121 and at least one non-modulation unit. Each modulation unit 121 and each non-modulation unit respectively correspond to at least one induction unit 111 of the photoelectric detection layer 110. That is, the modulation unit 121 and the induction unit 111 can be set in a one-to-one correspondence, or in a one-to-many setting, or even in a many-to-one setting. The non-modulation unit and the induction unit 111 can be set in a one-to-one correspondence, or in a one-to-many setting, or even in a many-to-one setting.

[0070] This working principle can be understood as follows: assuming that the incident optical signal is a vector X = [X1, X2, …… XN]T, and the signal received by the induction unit of the photoelectric detection layer is a vector Y = [Y1, Y2, …… YM]T. Correspondingly, Y = DX + W, where the conversion matrix D is determined by the optical modulation layer, and the vector W is noise. In the actual application of the spectral chip, it is necessary to calibrate the spectral chip first to obtain the conversion matrix D, and then use the calibrated spectral chip to measure the spectral information of the measured target. That is, using the known conversion matrix D and the vector Y obtained by the induction unit to solve the spectral signal X of the measured target.

[0071] However, the inventor of the present application has found that there are some problems in the actual application of the computational spectral chip working based on this principle, and these problems will affect the spectral detection performance of the spectral chip.

[0072] First, the inventors of the present application found that in practical applications, the computational spectral chip is relatively sensitive to the main optical angle of the incident optical signal. In actual use, changes in the main optical angle of the incident optical signal will significantly affect the accuracy of spectral recovery. Here, the main optical angle at any specific position of the spectral chip represents the angle between the main ray of the optical signal guided to the spectral chip and the normal line, where the main ray represents the line connecting the point emitting the optical signal from the object to be photographed and the corresponding photosensitive unit reaching the spectral chip, and the normal line represents the line perpendicular to the photosensitive surface of the spectral chip. Specifically, for the spectral chip, the angles of the main optical angles of different sensing units are allowed to have a large difference, but the light rays incident on the same sensing unit need to maintain a small angular difference.

[0073] Secondly, the inventors of the present application also found that in practical applications, the computational spectral chip is also relatively sensitive to the light collection cone angle at which the incident optical signal reaches each position of the spectral chip. In practical applications, if the light collection cone angle of the incident optical signal changes greatly, it will significantly affect the accuracy of spectral recovery.

[0074] Specifically, when the incident optical signal reaches a certain sensing unit of the spectral chip, if the incident angle of the optical signal to this sensing unit of the spectral chip (for this sensing unit, this incident angle can also be defined as the light collection cone angle of this sensing unit) changes, the parameter value at the corresponding position in the conversion matrix D will also change correspondingly, thereby affecting the accuracy of spectral recovery.

[0075] That is, due to the angular sensitivity of the light modulation layer, during the process of computational reconstruction, the conversion matrix D is affected by the main optical angle and / or the light collection cone angle of the incident optical signal. In the actual use environment, the spatial distribution of the light to be measured and the angular distribution of the light rays are uncertain. Therefore, the main optical angles and the light collection cone angles of the incident optical signals to different sensing units of the spectral chip are also uncertain, resulting in a large error in spectral measurement.

[0076] Verified by experimental data, the inventors of the present application found that: in the actual application process, the conversion matrix D of the spectral chip is not invariant, and it is affected by the main optical angle and the light collection cone angle. Further, when the light collection cone angle of the incident optical signal is large, it is equivalent to the superposition of the quasi-collimated light transmission spectra incident at multiple angles. At this time, the randomness and complexity of the spectrum transmitted by the light modulation layer decrease, and the correlation between different light modulation units increases, resulting in a decrease in the spectral recovery effect; on the contrary, the smaller the light collection cone angle, the better the spectral recovery effect.

[0077] Second, in the above technology, the information collected at different positions of the spectral chip (such as different sensing units on the photodetector layer) is assumed to originate from a certain point of the target to be measured, and then data processing is carried out to obtain the spectral information of the object to be measured. However, in actual application scenarios, the complexity of the environment and the object to be measured may cause deviations in the above assumptions, thereby resulting in relatively large errors in the spectral measurement effect.

[0078] For the first problem, the inventors of the present application propose a solution. Specifically, when using and calibrating the spectral chip, ensure that the angle of the main optical angle of the incident optical signal to each sensing unit of the spectral chip remains consistent, that is, the main optical angle of the optical signal guided to each position of the spectral chip is a fixed value. Here, the fact that the angle value of the main optical angle is a fixed value does not mean that the main optical angles of each photosensitive unit are exactly equal in different working processes, but rather that the value of the main optical angle is maintained within a predetermined range in different working processes, for example, within a range of ±5°. Further, in order to optimize the spectral recovery performance of the spectral chip, it is also necessary to ensure that the light collection cone angle of the incident optical signal guided to each position of the spectral chip is a predetermined value, and the predetermined value is less than or equal to 45°. Here, the fact that the light collection cone angle of the incident optical signal guided to each position of the spectral chip is a predetermined value does not mean that the light collection cone angles of each photosensitive unit are exactly equal in different working processes, but rather that the value of the light collection cone angle at each position is maintained within a predetermined range in different working processes, for example, within a range of ±5°. For example, when the imaging system has functions such as focusing, zooming, or defocusing, due to certain changes in the focus or focal length of the optical system, at this time, the main optical angle and the light collection cone angle will change to a certain extent, but this change will be within a predetermined range and will not affect the system performance. Therefore, it can also be understood that the corresponding main optical angle of the system is a fixed value and the light collection cone angle is a predetermined value.

[0079] Further, when the spectral chip is used in conjunction with an optical component, the optical component has a special structural configuration such that the optical signal guided to the spectral chip has a fixed principal light angle and a light-receiving light cone angle with a predetermined angle. After testing, the range of this preset angle is less than or equal to 45°, preferably less than or equal to 35°. Preferably, in some scenarios with a longer back focal length, the preset angle is preferably 10°-15°; in some scenarios with a larger field of view angle, the preset angle can also be 35°-40°. It is worth mentioning that the light-receiving light cone angle has a certain tolerance, but generally it should be controlled within ±5°. That is, through the optical component with a specific structural configuration, the principal light angle and the light-receiving light cone angle of each sensing unit of the spectral chip are controlled. Generally speaking, the principal light angle should take a fixed value, the light-receiving light cone angle is a predetermined angle, and the predetermined angle is less than or equal to 45°. To reduce the spectral recovery error of the spectral chip.

[0080] In some examples, it is also possible to separately control only the principal light angle or only the light-receiving light cone angle, that is, one of them is a predetermined value, and this is not limited to the present application.

[0081] Regarding the second problem, the inventors of the present application found that: in the process of spectral recovery through the spectral chip, in order to achieve better results, it is necessary to ensure the randomness and complexity of the transmission spectrum of the light modulation layer, and the correlation between the transmission spectra of different modulation units is relatively low. Among them, randomness and complexity can be characterized by the degree of rapid spectral change within a specific frequency domain range.

[0082] After experimental testing, as Figures 2A through 2I shown respectively represent the test charts of the projection performance curves of the spectral chip corresponding to the incident angles of 20°, 15°, 10°, 5°, 0°, -5°, -10°, -15°, -20°. Among them, the horizontal axis is the wavelength, the unit is micrometer, and the vertical axis is the absolute value of the light intensity. It should be noted that due to the angle sensitivity of the spectral chip, that is, when light signals with different angles are incident, the transmission spectra of the light modulation layer change greatly. It can be inferred from this that when the light-receiving light cone angle is larger, the randomness and complexity of the transmission spectrum of the light modulation layer decrease, and the correlation between different modulation units increases, resulting in a decrease in the spectral recovery effect; while when the light-receiving light cone angle is smaller, the randomness and complexity of the transmission spectrum of the light modulation layer increase, and the correlation between different modulation units decreases, thereby improving the spectral recovery effect.

[0083] Through further experiments, the inventors of the present application found that when the light-receiving light cone angle of each sensing unit of the spectral chip is less than or equal to 45°, the spectral recovery effect is better. That is, it has relatively high randomness and complexity of the transmitted spectrum and low correlation between different modulation units. According to the test of the experiment, the smaller the light-receiving light cone angle, the better the effect. Preferably, the angle of the light-receiving light cone angle is less than or equal to 10°.

[0084] Based on this, the present application provides an optical system, which includes: a spectral chip and an optical component held on the sensing path of the spectral chip. The spectral chip includes a photoelectric detection layer and a light modulation layer located on the sensing path of the photoelectric detection layer. The optical component is configured to receive a light signal from a photographed target and guide the light signal to the spectral chip. Among them, the optical component is configured such that the principal light angle of the light signal guided to each position of the spectral chip is a fixed value and the light-receiving light cone angle of each position is a predetermined value, and the predetermined value is less than or equal to 45°. That is, through the optical component with a specific structural configuration, the light-receiving light cone angle of each pixel point of the spectral chip is controlled to be a predetermined value within a predetermined range, and the principal light angle of the light signal corresponding to each pixel point is a fixed value to reduce the spectral recovery error of the spectral chip.

[0085] After introducing the basic principle of the present application, various non-limiting embodiments of the functions of the present application will be specifically introduced with reference to the accompanying drawings.

[0086] Exemplary Optical System

[0087] As Figure 3 shown, the optical system according to an embodiment of the present application is illustrated, which includes: a spectral chip 100 and an optical component 200 held on the sensing path of the spectral chip 100.

[0088] In a specific example of the present application, the spectral chip 100 includes a photoelectric detection layer 110 and a light modulation layer 120 located on the sensing path of the photoelectric detection layer 110. The light modulation layer 120 includes at least one modulation unit 121 and at least one non-modulation unit. The modulation unit 121 is used to modulate the light signal from the measured target. The light modulation layer 120 can be a structure or material with light filtering characteristics such as a metasurface, a photonic crystal, a nanorod, a multilayer film, a dye, a quantum dot, a MEMS, an FP etalon, a cavity layer, a waveguide layer, a diffraction element, etc.

[0089] To solve the two technical problems found in the application overview section, in particular, in the embodiments of the present application, the optical component 200 is configured such that the principal optical angle of the optical signal guided to each position of the spectral chip 100 is a fixed value and the light-receiving light cone angle of each position is a predetermined value, and the predetermined value is less than or equal to 45°. That is, in the embodiments of the present application, the optical component 200 has a structural configuration such that the principal optical angle of the optical signal guided to each position of the spectral chip 100 is a fixed value and the light-receiving light cone angle of each position is a predetermined value, where the predetermined value is less than or equal to 45°. In this way, the light-receiving light cone angle of each pixel of the spectral chip 100 is controlled to be a predetermined value within a preset range and / or the principal optical angle of each pixel of the spectral chip 100 is controlled to be a fixed value to reduce the spectral recovery error of the spectral chip 100.

[0090] It should be particularly noted that in the embodiments of the present application, the smaller the predetermined value of the light-receiving light cone angle, the better the spectral recovery effect of the spectral chip 100. Preferably, in the embodiments of the present application, the predetermined value is less than or equal to 35°, and more preferably, the predetermined value is less than or equal to 10°.

[0091] In the embodiments of the present application, the angular sensitivity of the spectral chip 100 can be reflected by the change in the principal optical angle and the change in the received light cone angle. To ensure the above technical effects, through experiments, it is known that in the embodiments of the present application, the change in the principal optical angle is less than or equal to 5°, that is, for each pixel of the spectral chip 100, the change in the value of the corresponding principal optical angle during different working processes is less than or equal to 5°, preferably less than or equal to 1°. And, the change in the light-receiving light cone angle is less than or equal to 1°, that is, for each pixel of the spectral chip 100, the change in the value of the corresponding light-receiving light cone angle during different working processes is less than or equal to 1°. In this way, the light modulation layer 120 of the spectral chip 100 has a relatively better modulation effect to obtain a relatively better spectral recovery effect. And, during the working process, the light-receiving light cone angle of each pixel of the spectral chip 100 needs to be maintained at a predetermined value and the smaller the predetermined value, the more beneficial it is to the spectral recovery of the spectral chip 100.

[0092] Based on different application scenarios and application requirements, the optical system according to the embodiments of the present application can be applied as a spectrometer, a spectral imaging device, or other image sensing devices.

[0093] Specifically, when the optical system is applied as a spectrometer, in a specific example of the present application, the optical component 200 is implemented as a lens group 210A, and the lens group 210A includes at least one optical lens for converging the incident optical signal, as Figure 4 shown.

[0094] For ease of explanation, in this application, the size of the target to be measured is defined as X cm * X cm, and the test distance is Y. Preferably, X is less than or equal to 6 cm, and Y is less than or equal to 10 cm. That is, when X is less than or equal to 6 cm and Y is less than or equal to 10 cm, the spectral chip 100 is adapted to be configured to collect the optical frequency information in the optical signal from the photographed target.

[0095] Further, assuming that the lens group 210A has a field of view angle θ and an image height h, the optical system applied as a spectrometer satisfies the following relationship: L / h * tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the photographed target, and L is the side length of the sensing effective area of the spectral chip 100.

[0096] In a specific example of this embodiment, the side length of the sensing effective area of the spectral chip 100 is 1.2 mm, the field of view angle θ of the lens group 210A is 23.5°, the image height h is 10 mm, the working distance is 60 mm, and the size of the target to be measured is 3 mm * 3 mm.

[0097] It is worth mentioning that in this example, in order to match the size and range of the target to be measured, and on the other hand, to improve the measurement accuracy, the F number of the lens group 210A is greater than or equal to 1.8, preferably greater than or equal to 2.5. It is also worth mentioning that in some variant embodiments of this example, in order to control the F number, the lens group 210A further includes a diaphragm for adjusting the F number of the lens group 210A.

[0098] It is also worth mentioning that the optical system provided in this example will be applied to other terminal devices, such as smartphones, etc. At this time, there are also requirements for the size of the optical system, especially in the height direction. For example, taking the requirement in the height direction as an example, the height dimension of the optical system can be designed to be less than or equal to 10 mm. For example, the optical system can be configured as a periscope optical system, that is, the optical system further includes a light turning element (not shown in the figure), and the light turning element is used to turn the incident optical signal, for example, turn it by 90°, to reduce the overall height dimension of the optical system.

[0099] Further, as Figure 4 The optical system shown can also be applied as a spectral imaging device, that is, when the optical component 200 is implemented as the lens group 210A, the optical system can also be applied as a spectral imaging device.

[0100] Different from the above spectrometer, when the optical system is applied as a spectral imaging device, there is no need to set the shooting range, that is, the shooting range of the target to be measured does not need to be restricted. In addition, the lens group 210A forms a conjugate plane between the target to be measured and the spectral chip 100, significantly reducing the influence of different light-emitting positions on the same pixel of the spectral chip 100.

[0101] Furthermore, when the optical system is applied as a spectrometer, the optical component 200 can also be implemented as other optical structures.

[0102] As Figure 5 shown, in this example, the optical component 200 of the optical system is implemented as a light homogenizing component 210B. Among them, the light homogenizing component 210B is used to homogenize the optical signals at different angles and then collimate them, so that the light receiving cone angle of the optical signals reaching each position of the spectral chip 100 is a predetermined value and within a preset angle range (for example, less than or equal to 45°), and the light receiving cone angle of the optical signals at each position is a fixed value. It is worth mentioning that, ideally, the light receiving cone angle and the principal light angle of the collimated optical signals reaching the spectral chip 100 are 0°. However, in reality, since there is no perfect collimation system, there is a certain angle between the optical signal and the normal. However, regardless of whether this angle exists, in the optical system, the principal light angle and the light receiving cone angle of the incident light can be understood to meet the above parameter design requirements, that is, the principal light angle is a fixed angle, and the light receiving cone angle is a predetermined value and within a preset range.

[0103] In this example, the light homogenizing component 210B includes a light homogenizing module 211B and a collimating unit 212B located on the light output path of the light homogenizing module 211B. The light homogenizing module 211B is configured to homogenize the optical signals from the object to be photographed, and the collimating unit 212B is configured to collimate the homogenized optical signals. In the example shown in Figure 5 the light homogenizing module 211B includes a light homogenizing element 2111B and a diaphragm 2112B located on the light output path of the light homogenizing element 2111B. In particular, the diaphragm 2112B has a light passing hole, and the size of the light passing hole is 1 mm - 10 mm, preferably 2 mm - 5 mm. That is, the diaphragm 2112B has a light passing hole with a relatively small size to intercept a small part of the incident light. After passing through the collimating unit 212B, the incident optical signal approximately becomes a parallel light, so that the light receiving cone angle of the spectral chip 100 is close to 0°.

[0104] Figure 6 Another schematic diagram showing that the optical component 200 of the optical system according to the embodiment of the present application is implemented as a light homogenizing component 210B is illustrated. As Figure 6As shown, in this variant implementation, the light homogenizing component 210B includes a light homogenizing module 211B and a collimating unit 212B located on the light output path of the light homogenizing module 211B. The light homogenizing module 211B is configured to homogenize the light signal from the object to be photographed, and the collimating unit 212B is configured to collimate the homogenized light signal. In particular, the light homogenizing module 211B includes an integrating sphere 2113B, the integrating sphere 2113B having a light input port and a light output port, and the size of the light output port being smaller than the size of the light input port.

[0105] Figure 7 FIG. illustrates another schematic diagram in which the optical component 200 of the optical system according to an embodiment of the present application is implemented as a light homogenizing component 210B. As Figure 7 shown, in this variant implementation, the light homogenizing component 210B includes a light homogenizing module 211B and a collimating unit 212B located on the light output path of the light homogenizing module 211B. The light homogenizing module 211B is configured to homogenize the light signal from the object to be photographed, and the collimating unit 212B is configured to collimate the homogenized light signal. In particular, the light homogenizing module 211B includes a diaphragm 2112B, a scattering element 2114B located on the light output path of the diaphragm 2112B, and a light homogenizing rod 2115B (in some examples, the light homogenizing rod 2115B can be replaced by an optical fiber) located on the light output path of the scattering element 2114B, wherein one end of the light homogenizing rod 2115B is near the focal plane of the collimating unit 212B. It should be noted that, in the diaphragm 2112 of the present invention, there is an inclined inner surface, which extends away from the optical axis outward from the object side to the image side. Further, at least a part of the inner surface is a reflecting surface in order to increase the light intensity, so as to reflect part of the light beam, so that the light beam can enter the collimating unit 212B, thereby increasing the light intensity entering the spectral chip 100 and further improving the accuracy.

[0106] Optionally, in the example shown in Figure 7 FIG., optionally, the light homogenizing module 211B further includes at least one optical lens 2116B, such as a convex lens, located on the light input path of the diaphragm 2112B.

[0107] In particular, in another embodiment of the present application, the optical component 200 is implemented as a telecentric lens 210C. That is, in some embodiments, using the telecentric lens 210C as the optical component 200 has relatively significant advantages in specific application scenarios. Those of ordinary skill in the art should be aware that the telecentric lens 210C, as a special lens system, is characterized by placing a diaphragm with a relatively small light passing aperture on the image side (or object side) focal plane of the lens, such that only the light rays passing through the focal point can propagate. At this time, the incident (or outgoing) light rays on the object side (or image side) are approximately parallel light rays parallel to the principal optical axis. As Figures 8A - 8C , it is represented as the object-side telecentric lens 210C, the image-side telecentric lens 210C, and the double-sided telecentric lens 210C. For the object-side (image-side) telecentric lens 210C, the corresponding diaphragm is located on the image side (object side) focal plane, and its incident (outgoing) light rays on the object side (image side) are approximately parallel light rays parallel to the principal optical axis. By combining the two, a double-sided telecentric lens 210C can be formed, superimposing the effects of the object-side and image-side telecentric lenses 210C.

[0108] In the optical system, by using the image-side telecentric lens 210C, it can be ensured that the principal light angle incident on any specific position on the spectral chip 100 is fixed, and the light collection cone angle is a relatively small predetermined value. If the object-side telecentric lens 210C is used, the requirements for the type of the light source to be measured can be reduced. If the double-sided telecentric lens 210C is used, it has both of the above two advantages. In actual applications, factors such as the aperture size and length of the optical system need to be comprehensively considered.

[0109] In summary, the optical system according to the embodiments of the present application is described, where the optical system includes a spectral chip 100 and an optical component 200 held on the sensing path of the spectral chip 100. The optical component 200 has a structural configuration such that the principal light angle of the light signal guided to each position on the spectral chip 100 is a fixed value and the light collection cone angle at each position is a predetermined value. In this way, through the optical component 200 with a specific structural configuration, the light collection cone angle of each pixel point on the spectral chip 100 is controlled to be a predetermined value within a preset range and / or the principal light angle of each pixel point is a fixed value, so as to reduce the spectral recovery error of the spectral chip 100

[0110] Design Method of the Exemplary Optical System

[0111] Accordingly, according to another aspect of the present application, there is also provided a design method for an optical system, which includes: S110, obtaining a conversion matrix of a photoelectric detection layer of a spectral chip, where the photoelectric detection layer obtains a detected optical signal from an incident optical signal based on the conversion matrix, and wherein the spectral chip further includes an optical modulation layer located on a sensing path of the photoelectric detection layer; and S120, determining a structural configuration of an optical component based on a numerical change of the conversion matrix, where the structural configuration is for making the chief ray angle of the optical signal guided to each position of the spectral chip a fixed value and the light collection cone angle of each position a predetermined value, and wherein the optical component is held on the sensing path of the spectral chip for receiving an optical signal from a photographed target and guiding the optical signal to the spectral chip.

[0112] In step S110, as described above, the spectral chip is sensitive to the angle of the incident optical signal, and this sensitivity can be quantitatively characterized by the chief ray angle and the light collection cone angle of the incident optical signal. Specifically, when the incident optical signal arrives at a certain sensing unit of the spectral chip, if the incident angle of the optical signal to this sensing unit of the spectral chip (for this sensing unit, this incident angle can also be defined as the light collection cone angle of this sensing unit) and the chief ray angle change, the parameter value at the corresponding position in the conversion matrix D will also change correspondingly, thereby affecting the accuracy of spectral recovery.

[0113] Accordingly, a computing device can be used to obtain the conversion matrix of the photoelectric detection layer of the spectral chip. Further, by adjusting the values of the chief ray angle and the light collection cone angle, and observing the changes in the values at each position in the conversion matrix and the final spectral recovery effect of the spectral chip. In this way, through simulation experiments and actual application requirements, the parameter selection of the chief ray angle and the light collection cone angle can be determined.

[0114] After determining the parameter selection of the chief ray angle and the light collection cone angle, the structural configuration of the optical component can be further determined, which is also the content in step S120.

[0115] In the design method of the optical system according to the present application, in one example, the predetermined value is less than or equal to 45°.

[0116] In the design method of the optical system according to the present application, in one example, the predetermined value is less than or equal to 35°.

[0117] In the design method of the optical system according to the present application, in one example, the predetermined value is less than or equal to 10°.

[0118] In a design method of an optical system according to the present application, in one example, the optical component includes a lens group, and the F-number of the lens group is greater than or equal to 1.8.

[0119] In a design method of an optical system according to the present application, in one example, the F-number of the lens group is greater than or equal to 2.5.

[0120] In a design method of an optical system according to the present application, in one example, the lens group has a field of view angle θ and an image height h, where the optical system satisfies the following relationship:

[0121] L / h * tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the object to be photographed, and L is the side length of the sensing effective area of the spectral chip.

[0122] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the drawings are only examples and do not limit the present invention. The object of the present invention has been fully and effectively achieved. The function and structural principle of the present invention have been shown and described in the embodiments, and the embodiments of the present invention can have any deformation or modification without departing from the principle.

Claims

1. An optical system, characterized in that, Comprising: A spectral chip, including a photoelectric detection layer and a light modulation layer located on the sensing path of the photoelectric detection layer, the photoelectric detection layer being configured to obtain a light signal modulated by the light modulation layer; And An optical component held on the sensing path of the spectral chip, the optical component being configured to receive a light signal from a photographed target and guide the light signal to the spectral chip; Wherein, the optical component is configured such that the principal light angle of the light signal guided to each position of the spectral chip is a fixed value and the light receiving light cone angle of each position is a predetermined value; the principal light angle of any position of the spectral chip represents the included angle between the principal light ray of the light signal guided to the spectral chip and the normal line, wherein the principal light ray represents the connection line between the point emitting the light signal from the photographed target and the point reaching the corresponding photosensitive unit of the spectral chip, and the normal line represents the line perpendicular to the photosensitive surface of the spectral chip; the light receiving light cone angle represents the incident angle of the light signal to the sensing unit of the spectral chip when the incident light signal reaches a certain sensing unit of the spectral chip; The optical component includes a lens group; or, the optical component includes a light homogenizing module and a collimating unit located on the light output path of the light homogenizing module, the light homogenizing module being configured to homogenize the light signal from the photographed target, and the collimating unit being configured to collimate the homogenized light signal; or, the optical component includes a telecentric lens.

2. The optical system according to claim 1, wherein, The predetermined value is less than or equal to 45°.

3. The optical system according to claim 2, wherein, The predetermined value is less than or equal to 35°.

4. The optical system according to claim 3, wherein, The predetermined value is less than or equal to 10°.

5. The optical system according to claim 2, wherein, The optical component includes a lens group, and the F-number of the lens group is greater than or equal to 1.

8.

6. The optical system according to claim 5, wherein, The F-number of the lens group is greater than or equal to 2.

5.

7. The optical system according to claim 5, wherein, The optical component further includes a diaphragm for adjusting the F-number of the lens group.

8. The optical system according to claim 5, wherein, The lens group has a field of view angle θ and an image height h, wherein the optical system satisfies the following relationship: L / h * tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the photographed target, and L is the side length of the sensing effective area of the spectral chip.

9. The optical system according to claim 8, wherein, X is less than or equal to 6 cm, Y is less than or equal to 10 cm, wherein when X is less than or equal to 6 cm and Y is less than or equal to 10 cm, the spectral chip is adapted to be configured to collect the optical frequency information in the light signal from the photographed target.

10. The optical system according to claim 4, wherein, The optical component includes a light homogenizing module and a collimating unit located on the light output path of the light homogenizing module, the light homogenizing module being configured to homogenize the light signal from the photographed target, and the collimating unit being configured to collimate the homogenized light signal.

11. The optical system according to claim 10, wherein, The light homogenizing module includes a diffusing element and a diaphragm located on the light output path of the diffusing element, the diaphragm having a light passing hole, and the size of the light passing hole is 1 mm to 10 mm.

12. The optical system according to claim 10, wherein, The light homogenizing module includes an integrating sphere, the integrating sphere having a light input port and a light output port, and the size of the light output port is smaller than the size of the light input port.

13. The optical system according to claim 10, wherein, The homogenizing module includes a diaphragm, a scattering element located on the light output path of the diaphragm, and a light homogenizing rod located on the light output path of the scattering element.

14. The optical system according to claim 13, wherein, The homogenizing module further includes at least one optical lens located on the light input path of the diaphragm.

15. The optical system according to claim 2, wherein, The optical assembly includes a telecentric lens.

16. A design method for an optical system, characterized in that, Comprising: Obtaining a conversion matrix of the photoelectric detection layer of the spectral chip, where the photoelectric detection layer obtains a detected optical signal from an incident optical signal based on the conversion matrix. Wherein, the spectral chip further includes a light modulation layer located on the sensing path of the photoelectric detection layer; and Determining the structural configuration of the optical assembly based on the numerical change of the conversion matrix, where the structural configuration is used to make the principal light angle of the optical signal guided to each position of the spectral chip a fixed value and the light receiving light cone angle of each position a predetermined value. Wherein, the optical assembly is held on the sensing path of the spectral chip, and is used to receive an optical signal from a photographed target and guide the optical signal to the spectral chip; the principal light angle of any position of the spectral chip represents the included angle between the principal ray of the optical signal guided to the spectral chip and the normal line, where the principal ray represents the connection line between the point emitting the optical signal from the photographed target and the point reaching the corresponding photosensitive unit of the spectral chip, and the normal line represents the line perpendicular to the photosensitive surface of the spectral chip; the light receiving light cone angle represents the incident angle of the optical signal to the sensing unit of the spectral chip when the incident optical signal reaches a certain sensing unit of the spectral chip.

17. The design method of the optical system according to claim 16, wherein, The predetermined value is less than or equal to 45°.

18. The design method of the optical system according to claim 17, wherein, The predetermined value is less than or equal to 35°.

19. The design method of the optical system according to claim 18, wherein, The predetermined value is less than or equal to 10°.

20. The design method of the optical system according to claim 16, wherein, The optical assembly includes a lens group, and the F-number of the lens group is greater than or equal to 1.

8.

21. The design method of the optical system according to claim 20, wherein, The F-number of the lens group is greater than or equal to 2.

5.

22. The design method of the optical system according to claim 21, wherein, The lens group has a field of view angle θ and an image height h, where the optical system satisfies the following relationship: L / h * tan(θ / 2) = (X / 2) / Y, where X represents the side length of the detection range of the optical system, Y represents the distance between the optical system and the photographed target, and L is the side length of the sensing effective area of the spectral chip.

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